Caesar Cipher

[XML] [Smart Pascal] [JavaScript] [PHP] [Lua] [Dart] [Output]

This example encrypts lower case letters only by the "Caesar" or "shift" cipher. This moves each letter onwards by a fixed number of letters in the alphabet, looping round from z to a. The unencrypted or decrypted text is known as plaintext and the encrypted form is ciphertext.

See below the blocks, the XML representation of the blocks and the generated Smart Pascal code. We have used the Blockly playground to generate from the same blocks JavaScript, Python, PHP, Lua and Dart.

The blocks

The blocks

XML Code of Blocks

<xml xmlns="http://www.w3.org/1999/xhtml">
  <block type="procedures_defreturn" id="$xTh]8/+)3Hx,^86@Jub" x="-37" y="-737">
    <mutation>
      <arg name="strPlaintext"></arg>
      <arg name="intDelta"></arg>
    </mutation>
    <field name="NAME">Encrypt</field>
    <comment pinned="false" h="80" w="160">Encrypts with Caesar cipher</comment>
    <statement name="STACK">
      <block type="variables_set" id="|75zxK7zZMue6?2^94SU">
        <field name="VAR">strCiphertext</field>
        <value name="VALUE">
          <block type="text" id="tp.IvQt057,Ubp,}o!;]">
            <field name="TEXT"></field>
          </block>
        </value>
        <next>
          <block type="controls_for" id="La7};p(HWo[!+DHvwODR">
            <field name="VAR">i</field>
            <value name="FROM">
              <shadow type="math_number" id="8H/l-_jGG=.7kR,dr-e2">
                <field name="NUM">1</field>
              </shadow>
            </value>
            <value name="TO">
              <shadow type="math_number" id="J[FixDyYdo:!BpI~hq,J">
                <field name="NUM">10</field>
              </shadow>
              <block type="text_length" id="mqAmXLyJ?f~harsKJRMI">
                <value name="VALUE">
                  <shadow type="text" id="[A8ucx9;)3P%%`j_@5lr">
                    <field name="TEXT">abc</field>
                  </shadow>
                  <block type="variables_get" id="[Q^PY%Kzg1Lv@-C.aU(J">
                    <field name="VAR">strPlaintext</field>
                  </block>
                </value>
              </block>
            </value>
            <value name="BY">
              <shadow type="math_number" id="LBO9bAe.9oZ[c3#F4lbF">
                <field name="NUM">1</field>
              </shadow>
            </value>
            <statement name="DO">
              <block type="variables_set" id="{NCNrJuJ2Vnwqs~S3)84">
                <field name="VAR">strCurrentChar</field>
                <value name="VALUE">
                  <block type="text_charAt" id="XJFh)2Cz{S-Do|xLHA5+">
                    <mutation at="true"></mutation>
                    <field name="WHERE">FROM_START</field>
                    <value name="VALUE">
                      <block type="variables_get" id="2fw04iVKX`ao=9F{7^),">
                        <field name="VAR">strPlaintext</field>
                      </block>
                    </value>
                    <value name="AT">
                      <block type="variables_get" id="o!,G(}V$K~-HF|kJuxg3">
                        <field name="VAR">i</field>
                      </block>
                    </value>
                  </block>
                </value>
                <next>
                  <block type="variables_set" id="/PEY$Wo6?qs:}A@.Oii-">
                    <field name="VAR">intPosition</field>
                    <value name="VALUE">
                      <block type="text_indexOf" id="#)?jUiMf/{3/*jO+Hm@w">
                        <field name="END">FIRST</field>
                        <value name="VALUE">
                          <block type="variables_get" id="9piBu5,P$4.a@)avG1@_">
                            <field name="VAR">strAlphaLower</field>
                          </block>
                        </value>
                        <value name="FIND">
                          <shadow type="text" id="|*T4}~ru}Z1^fyOZ=E4D">
                            <field name="TEXT">abc</field>
                          </shadow>
                          <block type="variables_get" id="a?p4v`(%l!+%a/A=zYpD">
                            <field name="VAR">strCurrentChar</field>
                          </block>
                        </value>
                      </block>
                    </value>
                    <next>
                      <block type="controls_if" id="mfv=W8]lj5hB9/_b3gmt">
                        <value name="IF0">
                          <block type="logic_compare" id="!9HuV?8nurV$Zf]M%hDp">
                            <field name="OP">LT</field>
                            <value name="A">
                              <block type="variables_get" id="Chk8)}Js7N*Mwslu5*a1">
                                <field name="VAR">intPosition</field>
                              </block>
                            </value>
                            <value name="B">
                              <block type="math_number" id="_z@uS9XDUpK@1^3[AM~`">
                                <field name="NUM">1</field>
                              </block>
                            </value>
                          </block>
                        </value>
                        <statement name="DO0">
                          <block type="text_append" id="[.VFyQ#9gwwAF}*^o}n6">
                            <field name="VAR">strCiphertext</field>
                            <value name="TEXT">
                              <shadow type="text" id="|7Sn@K|(_m*;;NH]X=QC">
                                <field name="TEXT"></field>
                              </shadow>
                              <block type="variables_get" id="3/0;-Di|q,B3W6%tXXO6">
                                <field name="VAR">strCurrentChar</field>
                              </block>
                            </value>
                            <next>
                              <block type="controls_flow_statements" id="TlYVR-GnJb!Y^aX_;:4_">
                                <field name="FLOW">CONTINUE</field>
                              </block>
                            </next>
                          </block>
                        </statement>
                        <next>
                          <block type="variables_set" id="!V*%n:+,p5q8]bHG~,^t">
                            <field name="VAR">intPosition</field>
                            <value name="VALUE">
                              <block type="math_arithmetic" id="Pt|PGS;t@e]vLW,i/8,]">
                                <field name="OP">ADD</field>
                                <value name="A">
                                  <shadow type="math_number" id="=Qi1nCuhqr~Jc-s(t]=y">
                                    <field name="NUM">1</field>
                                  </shadow>
                                  <block type="variables_get" id="w4Ms,N%WJ;s/T{]!SN?M">
                                    <field name="VAR">intPosition</field>
                                  </block>
                                </value>
                                <value name="B">
                                  <shadow type="math_number" id="[:i7$D%tyjw`T!]T86rg">
                                    <field name="NUM">8</field>
                                  </shadow>
                                  <block type="variables_get" id="iek|0j%;(:aH3rbW4H/F">
                                    <field name="VAR">intDelta</field>
                                  </block>
                                </value>
                              </block>
                            </value>
                            <next>
                              <block type="controls_if" id="?*P:`78+S|OsMrv)varl">
                                <value name="IF0">
                                  <block type="logic_compare" id="kUVB)L6TvtsYv}#7@.zW">
                                    <field name="OP">GT</field>
                                    <value name="A">
                                      <block type="variables_get" id="JwfG:eR{a)8EMD.:p9{v">
                                        <field name="VAR">intPosition</field>
                                      </block>
                                    </value>
                                    <value name="B">
                                      <block type="math_number" id="Af;$CNJNW(G}}4oX2U?i">
                                        <field name="NUM">26</field>
                                      </block>
                                    </value>
                                  </block>
                                </value>
                                <statement name="DO0">
                                  <block type="math_change" id="ZBnxKCW^ynf/s/sxp.@%">
                                    <field name="VAR">intPosition</field>
                                    <value name="DELTA">
                                      <shadow type="math_number" id="t4Zfgv+^!;^=bE9LLDFj">
                                        <field name="NUM">1</field>
                                      </shadow>
                                      <block type="math_number" id="o-xrPa)UIC!*`UN7IG%i">
                                        <field name="NUM">-26</field>
                                      </block>
                                    </value>
                                  </block>
                                </statement>
                                <next>
                                  <block type="variables_set" id="IR5qd5eWp+{CX0m7jV3+">
                                    <field name="VAR">strCurrentChar</field>
                                    <value name="VALUE">
                                      <block type="text_charAt" id="?f[Ro1)*.w_J/LN:,A)v">
                                        <mutation at="true"></mutation>
                                        <field name="WHERE">FROM_START</field>
                                        <value name="VALUE">
                                          <block type="variables_get" id="=U``dg_!A7-wAna:(?gI">
                                            <field name="VAR">strAlphaLower</field>
                                          </block>
                                        </value>
                                        <value name="AT">
                                          <block type="variables_get" id="`e?7LI.E#++:QYw#*T[T">
                                            <field name="VAR">intPosition</field>
                                          </block>
                                        </value>
                                      </block>
                                    </value>
                                    <next>
                                      <block type="text_append" id="wec;h{S,07W)kIiaWe#s">
                                        <field name="VAR">strCiphertext</field>
                                        <value name="TEXT">
                                          <shadow type="text" id="|7Sn@K|(_m*;;NH]X=QC">
                                            <field name="TEXT"></field>
                                          </shadow>
                                          <block type="variables_get" id="/zii2=SAn.C`#%Zp:kkj">
                                            <field name="VAR">strCurrentChar</field>
                                          </block>
                                        </value>
                                      </block>
                                    </next>
                                  </block>
                                </next>
                              </block>
                            </next>
                          </block>
                        </next>
                      </block>
                    </next>
                  </block>
                </next>
              </block>
            </statement>
          </block>
        </next>
      </block>
    </statement>
    <value name="RETURN">
      <block type="variables_get" id="F2]|JPA5#t,~h9,qOHER">
        <field name="VAR">strCiphertext</field>
      </block>
    </value>
  </block>
  <block type="procedures_defreturn" id="2}gB@{Z+,AxVCjhf,1G{" x="-37" y="-237">
    <mutation>
      <arg name="strCiphertext"></arg>
      <arg name="intDelta"></arg>
    </mutation>
    <field name="NAME">Decrypt</field>
    <comment pinned="false" h="80" w="160">Decrypts Caesar cipher</comment>
    <statement name="STACK">
      <block type="variables_set" id="L;IBd6$Tkqwzqe`$@`v{">
        <field name="VAR">strPlaintext</field>
        <value name="VALUE">
          <block type="text" id="`Do(|!v[vCDgaQrcYwi0">
            <field name="TEXT"></field>
          </block>
        </value>
        <next>
          <block type="controls_for" id="O|/Kh*;^K?t)z3+QGGJ9">
            <field name="VAR">i</field>
            <value name="FROM">
              <shadow type="math_number" id="+aGXFjNf10j#b|/Izg-?">
                <field name="NUM">1</field>
              </shadow>
            </value>
            <value name="TO">
              <shadow type="math_number" id="J[FixDyYdo:!BpI~hq,J">
                <field name="NUM">10</field>
              </shadow>
              <block type="text_length" id="Z[PHqLJfPPXh0=mbWOFm">
                <value name="VALUE">
                  <shadow type="text" id="[A8ucx9;)3P%%`j_@5lr">
                    <field name="TEXT">abc</field>
                  </shadow>
                  <block type="variables_get" id="zl2x10Q%ym?vp-xe1FE`">
                    <field name="VAR">strCiphertext</field>
                  </block>
                </value>
              </block>
            </value>
            <value name="BY">
              <shadow type="math_number" id="Ev]9B/iA`^XTO6lpj,(^">
                <field name="NUM">1</field>
              </shadow>
            </value>
            <statement name="DO">
              <block type="variables_set" id="y|bvJKj6%X#-4*v*Z+Ff">
                <field name="VAR">strCurrentChar</field>
                <value name="VALUE">
                  <block type="text_charAt" id="yPJQse3Tk1fN+u#k^w(B">
                    <mutation at="true"></mutation>
                    <field name="WHERE">FROM_START</field>
                    <value name="VALUE">
                      <block type="variables_get" id="sAa9$uT,uL.HI#l?sR74">
                        <field name="VAR">strCiphertext</field>
                      </block>
                    </value>
                    <value name="AT">
                      <block type="variables_get" id="p:poh;f[~mIaERpm2rYv">
                        <field name="VAR">i</field>
                      </block>
                    </value>
                  </block>
                </value>
                <next>
                  <block type="variables_set" id="AV`[3JI*z#9NgS3z%2H@">
                    <field name="VAR">intPosition</field>
                    <value name="VALUE">
                      <block type="text_indexOf" id="c=_7*o9l){2{$SB8rehE">
                        <field name="END">FIRST</field>
                        <value name="VALUE">
                          <block type="variables_get" id="#:jU-p9U@vft?y8?RGZ4">
                            <field name="VAR">strAlphaLower</field>
                          </block>
                        </value>
                        <value name="FIND">
                          <shadow type="text" id="|*T4}~ru}Z1^fyOZ=E4D">
                            <field name="TEXT">abc</field>
                          </shadow>
                          <block type="variables_get" id="]G){g#Le;%Ob:eZn.m7g">
                            <field name="VAR">strCurrentChar</field>
                          </block>
                        </value>
                      </block>
                    </value>
                    <next>
                      <block type="controls_if" id="]g%_L=P4,MO@UtO!cnDh">
                        <value name="IF0">
                          <block type="logic_compare" id="}~gB(g*C2Ni)CMT*^3;#">
                            <field name="OP">LT</field>
                            <value name="A">
                              <block type="variables_get" id="~gqFuMX/J-#P46_:)@n|">
                                <field name="VAR">intPosition</field>
                              </block>
                            </value>
                            <value name="B">
                              <block type="math_number" id="li;Kl7C.7@L/NspL4y(x">
                                <field name="NUM">1</field>
                              </block>
                            </value>
                          </block>
                        </value>
                        <statement name="DO0">
                          <block type="text_append" id="l7u*qv#xmli}[O%7)zdZ">
                            <field name="VAR">strPlaintext</field>
                            <value name="TEXT">
                              <shadow type="text" id="|7Sn@K|(_m*;;NH]X=QC">
                                <field name="TEXT"></field>
                              </shadow>
                              <block type="variables_get" id="M-D`QSks.ucP9I;u2KNf">
                                <field name="VAR">strCurrentChar</field>
                              </block>
                            </value>
                            <next>
                              <block type="controls_flow_statements" id="oBX7;GI-Y3K1-0R@!|!K">
                                <field name="FLOW">CONTINUE</field>
                              </block>
                            </next>
                          </block>
                        </statement>
                        <next>
                          <block type="variables_set" id="5ANCopDTGfEZnv[]`E}H">
                            <field name="VAR">intPosition</field>
                            <value name="VALUE">
                              <block type="math_arithmetic" id="4KL^*Ce;ej|o^rSaeb{+">
                                <field name="OP">ADD</field>
                                <value name="A">
                                  <shadow type="math_number" id="2?s6xI}9(@fuPgp-**a~">
                                    <field name="NUM">1</field>
                                  </shadow>
                                  <block type="math_arithmetic" id="7iCF%ByZ62TTh80vHeIX">
                                    <field name="OP">MINUS</field>
                                    <value name="A">
                                      <shadow type="math_number" id="=Qi1nCuhqr~Jc-s(t]=y">
                                        <field name="NUM">1</field>
                                      </shadow>
                                      <block type="variables_get" id="gvR6q`t3{T:=[v`3w=x7">
                                        <field name="VAR">intPosition</field>
                                      </block>
                                    </value>
                                    <value name="B">
                                      <shadow type="math_number" id="[:i7$D%tyjw`T!]T86rg">
                                        <field name="NUM">8</field>
                                      </shadow>
                                      <block type="variables_get" id="K(wIu0:4|Nk+Q7Eb#;_h">
                                        <field name="VAR">intDelta</field>
                                      </block>
                                    </value>
                                  </block>
                                </value>
                                <value name="B">
                                  <shadow type="math_number" id="U~v_CAK3IZ(c+FMZwK)K">
                                    <field name="NUM">26</field>
                                  </shadow>
                                </value>
                              </block>
                            </value>
                            <next>
                              <block type="controls_if" id="S?_}FqD8OY)DnpjU2Spv">
                                <value name="IF0">
                                  <block type="logic_compare" id="dv8:6/G3s?cQxpI9j!|n">
                                    <field name="OP">GT</field>
                                    <value name="A">
                                      <block type="variables_get" id="3g#tu!r}+TI^lmryMAGl">
                                        <field name="VAR">intPosition</field>
                                      </block>
                                    </value>
                                    <value name="B">
                                      <block type="math_number" id="}71*Z9hN#q5d{G:gU8Gt">
                                        <field name="NUM">26</field>
                                      </block>
                                    </value>
                                  </block>
                                </value>
                                <statement name="DO0">
                                  <block type="math_change" id="@G%eD(9vLxno.^WrM^72">
                                    <field name="VAR">intPosition</field>
                                    <value name="DELTA">
                                      <shadow type="math_number" id="t4Zfgv+^!;^=bE9LLDFj">
                                        <field name="NUM">1</field>
                                      </shadow>
                                      <block type="math_number" id=":lO2UhWC28]N!m$Yuuuk">
                                        <field name="NUM">-26</field>
                                      </block>
                                    </value>
                                  </block>
                                </statement>
                                <next>
                                  <block type="variables_set" id="yl!fE{$wc[eUf^4=-C$9">
                                    <field name="VAR">strCurrentChar</field>
                                    <value name="VALUE">
                                      <block type="text_charAt" id="Md]fg?lai@aNnh8FwQ@d">
                                        <mutation at="true"></mutation>
                                        <field name="WHERE">FROM_START</field>
                                        <value name="VALUE">
                                          <block type="variables_get" id="8l#HQ4%IQ,30,qWu@X-9">
                                            <field name="VAR">strAlphaLower</field>
                                          </block>
                                        </value>
                                        <value name="AT">
                                          <block type="variables_get" id="ji$S!m;!dlvJlc#jM_Y=">
                                            <field name="VAR">intPosition</field>
                                          </block>
                                        </value>
                                      </block>
                                    </value>
                                    <next>
                                      <block type="text_append" id="l}$0|4eg`P+Df7N1m=gv">
                                        <field name="VAR">strPlaintext</field>
                                        <value name="TEXT">
                                          <shadow type="text" id="|7Sn@K|(_m*;;NH]X=QC">
                                            <field name="TEXT"></field>
                                          </shadow>
                                          <block type="variables_get" id="9j_PMuE_7}zS$O6#6qXC">
                                            <field name="VAR">strCurrentChar</field>
                                          </block>
                                        </value>
                                      </block>
                                    </next>
                                  </block>
                                </next>
                              </block>
                            </next>
                          </block>
                        </next>
                      </block>
                    </next>
                  </block>
                </next>
              </block>
            </statement>
          </block>
        </next>
      </block>
    </statement>
    <value name="RETURN">
      <block type="variables_get" id="2EPt=/OZJDHQR1n{m@aG">
        <field name="VAR">strPlaintext</field>
      </block>
    </value>
  </block>
  <block type="variables_set" id="=H;=/^f(0A+]r$XA#GvJ" x="-38" y="263">
    <field name="VAR">strAlphaLower</field>
    <value name="VALUE">
      <block type="text" id="eF$H#Ry]w_N[!)h@ywgl">
        <field name="TEXT">abcdefghijklmnopqrstuvwxyz</field>
      </block>
    </value>
    <next>
      <block type="text_print" id="trtL@s/6ib1cRfVvwJ)-">
        <value name="TEXT">
          <shadow type="text" id="(`N_as[X.tNr]IZM#+Gl">
            <field name="TEXT">abc</field>
          </shadow>
          <block type="procedures_callreturn" id="C_g@f{a/6Bwq`0yQ^.R8">
            <mutation name="Encrypt">
              <arg name="strPlaintext"></arg>
              <arg name="intDelta"></arg>
            </mutation>
            <value name="ARG0">
              <block type="text" id="KfVw~?D8H+dtAUwm#.HC">
                <field name="TEXT">abcdefghijklmnopqrstuvwxyz</field>
              </block>
            </value>
            <value name="ARG1">
              <block type="math_number" id="YET[Fi^}nxuue.ew21:`">
                <field name="NUM">8</field>
              </block>
            </value>
          </block>
        </value>
        <next>
          <block type="text_print" id="+Q@7My+%80PGKRE4z988">
            <value name="TEXT">
              <shadow type="text" id="nsDP8}j^Gg%Hyq=Q%b70">
                <field name="TEXT">abc</field>
              </shadow>
              <block type="procedures_callreturn" id="T7.Hfw@9bv|Y?6g~kP;g">
                <mutation name="Decrypt">
                  <arg name="strCiphertext"></arg>
                  <arg name="intDelta"></arg>
                </mutation>
                <value name="ARG0">
                  <block type="variables_get" id="*cGPpxXGVAn[*Dxj][V5">
                    <field name="VAR">strCiphertext</field>
                  </block>
                </value>
                <value name="ARG1">
                  <block type="math_number" id="7e::tl7~QIdW^n4Dko4[">
                    <field name="NUM">8</field>
                  </block>
                </value>
              </block>
            </value>
            <next>
              <block type="text_print" id="-jskN+tsg`E+t}akyp`7">
                <value name="TEXT">
                  <shadow type="text" id="(`N_as[X.tNr]IZM#+Gl">
                    <field name="TEXT">abc</field>
                  </shadow>
                  <block type="procedures_callreturn" id="MdU4]UEMbY)7B5B~boiJ">
                    <mutation name="Encrypt">
                      <arg name="strPlaintext"></arg>
                      <arg name="intDelta"></arg>
                    </mutation>
                    <value name="ARG0">
                      <block type="text" id="9]2I/B5_9Qha{@nZA[Jh">
                        <field name="TEXT">The cat sat on the mat.</field>
                      </block>
                    </value>
                    <value name="ARG1">
                      <block type="math_number" id="TwXP+~UwgZZLY7_Iq_R!">
                        <field name="NUM">8</field>
                      </block>
                    </value>
                  </block>
                </value>
                <next>
                  <block type="text_print" id="5Kd}^Tx/!-V1Y`1vzH?j">
                    <value name="TEXT">
                      <shadow type="text" id="nsDP8}j^Gg%Hyq=Q%b70">
                        <field name="TEXT">abc</field>
                      </shadow>
                      <block type="procedures_callreturn" id="5n=`7w4TepK6@=anQm-x">
                        <mutation name="Decrypt">
                          <arg name="strCiphertext"></arg>
                          <arg name="intDelta"></arg>
                        </mutation>
                        <value name="ARG0">
                          <block type="variables_get" id="]K=ei]brh?X[ED^8yr3}">
                            <field name="VAR">strCiphertext</field>
                          </block>
                        </value>
                        <value name="ARG1">
                          <block type="math_number" id="gJlm=jD3pS*HqC#r`#.i">
                            <field name="NUM">8</field>
                          </block>
                        </value>
                      </block>
                    </value>
                  </block>
                </next>
              </block>
            </next>
          </block>
        </next>
      </block>
    </next>
  </block>
</xml>

Generated Smart Pascal Code

var intDelta: Integer;
var intPosition: Integer;
var stCiphertext: Variant;
var strAlphaLower: String;
var strCiphertext: String;
var strCurrentChar: String;
var strPlaintext: String;


{
  Encrypts with Caesar cipher
}
function Encrypt(strPlaintext: String; intDelta: Integer): String;
begin
  strCiphertext := '';
  for var i := 1 to length(strPlaintext) step 1 do
  begin
    strCurrentChar := CharAt(strPlaintext, (i - 1) + 1);
    intPosition := Pos(strCurrentChar, strAlphaLower);
    if ((intPosition < 1)) then
    begin
      strCiphertext += strCurrentChar;
      continue;
    end;
    intPosition := intPosition + intDelta;
    if ((intPosition > 26)) then
    begin
      intPosition += -26;
    end;
    strCurrentChar := CharAt(strAlphaLower, (intPosition - 1) + 1);
    strCiphertext += strCurrentChar;
  end;
  Result := strCiphertext;
end;


{
  Decrypts Caesar cipher
}
function Decrypt(strCiphertext: String; intDelta: Integer): String;
begin
  strPlaintext := '';
  for var i := 1 to length(strCiphertext) step 1 do
  begin
    strCurrentChar := CharAt(strCiphertext, (i - 1) + 1);
    intPosition := Pos(strCurrentChar, strAlphaLower);
    if ((intPosition < 1)) then
    begin
      strPlaintext += strCurrentChar;
      continue;
    end;
    intPosition := (intPosition - intDelta) + 26;
    if ((intPosition > 26)) then
    begin
      intPosition += -26;
    end;
    strCurrentChar := CharAt(strAlphaLower, (intPosition - 1) + 1);
    strPlaintext += strCurrentChar;
  end;
  Result := strPlaintext;
end;



strAlphaLower := 'abcdefghijklmnopqrstuvwxyz';
Console.writeln(Encrypt('abcdefghijklmnopqrstuvwxyz', 8));
Console.writeln(Decrypt(strCiphertext, 8));
Console.writeln(Encrypt('The cat sat on the mat.', 8));
Console.writeln(Decrypt(strCiphertext, 8));

Generated JavaScript Code

var strCiphertext, strCurrentChar, intPosition, strAlphaLower, intDelta, i, strPlaintext;

/**
 * Encrypts with Caesar cipher
 */
function Encrypt(strPlaintext, intDelta) {
  strCiphertext = '';
  var i_end = strPlaintext.length;
  var i_inc = 1;
  if (1 > i_end) {
    i_inc = -i_inc;
  }
  for (i = 1; i_inc >= 0 ? i <= i_end : i >= i_end; i += i_inc) {
    strCurrentChar = strPlaintext.charAt((i - 1));
    intPosition = strAlphaLower.indexOf(strCurrentChar) + 1;
    if (intPosition < 1) {
      strCiphertext = String(strCiphertext) + String(strCurrentChar);
      continue;
    }
    intPosition = intPosition + intDelta;
    if (intPosition > 26) {
      intPosition = (typeof intPosition == 'number' ? intPosition : 0) + -26;
    }
    strCurrentChar = strAlphaLower.charAt((intPosition - 1));
    strCiphertext = String(strCiphertext) + String(strCurrentChar);
  }
  return strCiphertext;
}

/**
 * Decrypts Caesar cipher
 */
function Decrypt(strCiphertext, intDelta) {
  strPlaintext = '';
  var i_end2 = strCiphertext.length;
  var i_inc2 = 1;
  if (1 > i_end2) {
    i_inc2 = -i_inc2;
  }
  for (i = 1; i_inc2 >= 0 ? i <= i_end2 : i >= i_end2; i += i_inc2) {
    strCurrentChar = strCiphertext.charAt((i - 1));
    intPosition = strAlphaLower.indexOf(strCurrentChar) + 1;
    if (intPosition < 1) {
      strPlaintext = String(strPlaintext) + String(strCurrentChar);
      continue;
    }
    intPosition = (intPosition - intDelta) + 26;
    if (intPosition > 26) {
      intPosition = (typeof intPosition == 'number' ? intPosition : 0) + -26;
    }
    strCurrentChar = strAlphaLower.charAt((intPosition - 1));
    strPlaintext = String(strPlaintext) + String(strCurrentChar);
  }
  return strPlaintext;
}


strAlphaLower = 'abcdefghijklmnopqrstuvwxyz';
window.alert(Encrypt('abcdefghijklmnopqrstuvwxyz', 8));
window.alert(Decrypt(strCiphertext, 8));
window.alert(Encrypt('The cat sat on the mat.', 8));
window.alert(Decrypt(strCiphertext, 8));

Generated Python Code

from numbers import Number

strCiphertext = None
strCurrentChar = None
intPosition = None
strAlphaLower = None
intDelta = None
i = None
strPlaintext = None

def upRange(start, stop, step):
  while start <= stop:
    yield start
    start += abs(step)

def downRange(start, stop, step):
  while start >= stop:
    yield start
    start -= abs(step)

"""Encrypts with Caesar cipher
"""
def Encrypt(strPlaintext, intDelta):
  global strCiphertext, strCurrentChar, intPosition, strAlphaLower, i
  strCiphertext = ''
  i_end = float(len(strPlaintext))
  for i in (1 <= i_end) and upRange(1, i_end, 1) or downRange(1, i_end, 1):
    strCurrentChar = strPlaintext[int(i - 1)]
    intPosition = strAlphaLower.find(strCurrentChar) + 1
    if intPosition < 1:
      strCiphertext = str(strCiphertext) + str(strCurrentChar)
      continue
    intPosition = intPosition + intDelta
    if intPosition > 26:
      intPosition = (intPosition if isinstance(intPosition, Number) else 0) + -26
    strCurrentChar = strAlphaLower[int(intPosition - 1)]
    strCiphertext = str(strCiphertext) + str(strCurrentChar)
  return strCiphertext

"""Decrypts Caesar cipher
"""
def Decrypt(strCiphertext, intDelta):
  global strCurrentChar, intPosition, strAlphaLower, i, strPlaintext
  strPlaintext = ''
  i_end2 = float(len(strCiphertext))
  for i in (1 <= i_end2) and upRange(1, i_end2, 1) or downRange(1, i_end2, 1):
    strCurrentChar = strCiphertext[int(i - 1)]
    intPosition = strAlphaLower.find(strCurrentChar) + 1
    if intPosition < 1:
      strPlaintext = str(strPlaintext) + str(strCurrentChar)
      continue
    intPosition = (intPosition - intDelta) + 26
    if intPosition > 26:
      intPosition = (intPosition if isinstance(intPosition, Number) else 0) + -26
    strCurrentChar = strAlphaLower[int(intPosition - 1)]
    strPlaintext = str(strPlaintext) + str(strCurrentChar)
  return strPlaintext


strAlphaLower = 'abcdefghijklmnopqrstuvwxyz'
print(Encrypt('abcdefghijklmnopqrstuvwxyz', 8))
print(Decrypt(strCiphertext, 8))
print(Encrypt('The cat sat on the mat.', 8))
print(Decrypt(strCiphertext, 8))

Generated PHP Code

$strCiphertext;
$strCurrentChar;
$intPosition;
$strAlphaLower;
$intDelta;
$i;
$strPlaintext;

function length($value) {
  if (is_string($value)) {
    return strlen($value);
  } else {
    return count($value);
  }
}

function text_indexOf($text, $search) {
  $pos = strpos($text, $search);
  return $pos === false ?  0 : $pos + 1;
}

// Encrypts with Caesar cipher
function Encrypt($strPlaintext, $intDelta) {
  global $strCiphertext, $strCurrentChar, $intPosition, $strAlphaLower, $i;
  $strCiphertext = '';
  $_i_end = length($strPlaintext);
  $_i_inc = 1;
  if (1 > $_i_end) {
    $_i_inc = -$_i_inc;
  }
  for ($i = 1; $_i_inc >= 0 ? $i <= $_i_end : $i >= $_i_end; $i += $_i_inc) {
    $strCurrentChar = substr($strPlaintext, ($i - 1), 1);
    $intPosition = text_indexOf($strAlphaLower, $strCurrentChar);
    if ($intPosition < 1) {
      $strCiphertext .= $strCurrentChar;
      continue;
    }
    $intPosition = $intPosition + $intDelta;
    if ($intPosition > 26) {
      $intPosition += -26;
    }
    $strCurrentChar = substr($strAlphaLower, ($intPosition - 1), 1);
    $strCiphertext .= $strCurrentChar;
  }
  return $strCiphertext;
}

// Decrypts Caesar cipher
function Decrypt($strCiphertext, $intDelta) {
  global $strCurrentChar, $intPosition, $strAlphaLower, $i, $strPlaintext;
  $strPlaintext = '';
  $_i_end2 = length($strCiphertext);
  $_i_inc2 = 1;
  if (1 > $_i_end2) {
    $_i_inc2 = -$_i_inc2;
  }
  for ($i = 1; $_i_inc2 >= 0 ? $i <= $_i_end2 : $i >= $_i_end2; $i += $_i_inc2) {
    $strCurrentChar = substr($strCiphertext, ($i - 1), 1);
    $intPosition = text_indexOf($strAlphaLower, $strCurrentChar);
    if ($intPosition < 1) {
      $strPlaintext .= $strCurrentChar;
      continue;
    }
    $intPosition = ($intPosition - $intDelta) + 26;
    if ($intPosition > 26) {
      $intPosition += -26;
    }
    $strCurrentChar = substr($strAlphaLower, ($intPosition - 1), 1);
    $strPlaintext .= $strCurrentChar;
  }
  return $strPlaintext;
}


$strAlphaLower = 'abcdefghijklmnopqrstuvwxyz';
print(Encrypt('abcdefghijklmnopqrstuvwxyz', 8));
print(Decrypt($strCiphertext, 8));
print(Encrypt('The cat sat on the mat.', 8));
print(Decrypt($strCiphertext, 8));

Generated Lua Code

function firstIndexOf(str, substr)
  local i = string.find(str, substr, 1, true)
  if i == nil then
    return 0
  else
    return i
  end
end

-- Encrypts with Caesar cipher
function Encrypt(strPlaintext, intDelta)
  strCiphertext = ''
  i_inc = 1
  if (1) > (#strPlaintext) then
    i_inc = -i_inc
  end
  for i = 1, #strPlaintext, i_inc do
    strCurrentChar = string.sub(strPlaintext, i, i)
    intPosition = firstIndexOf(strAlphaLower, strCurrentChar)
    if intPosition < 1 then
      strCiphertext = strCiphertext .. strCurrentChar
      goto continue
    end
    intPosition = intPosition + intDelta
    if intPosition > 26 then
      intPosition = intPosition + -26
    end
    strCurrentChar = string.sub(strAlphaLower, intPosition, intPosition)
    strCiphertext = strCiphertext .. strCurrentChar
    ::continue::
  end
  return strCiphertext
end


-- Decrypts Caesar cipher
function Decrypt(strCiphertext, intDelta)
  strPlaintext = ''
  i_inc2 = 1
  if (1) > (#strCiphertext) then
    i_inc2 = -i_inc2
  end
  for i = 1, #strCiphertext, i_inc2 do
    strCurrentChar = string.sub(strCiphertext, i, i)
    intPosition = firstIndexOf(strAlphaLower, strCurrentChar)
    if intPosition < 1 then
      strPlaintext = strPlaintext .. strCurrentChar
      goto continue
    end
    intPosition = (intPosition - intDelta) + 26
    if intPosition > 26 then
      intPosition = intPosition + -26
    end
    strCurrentChar = string.sub(strAlphaLower, intPosition, intPosition)
    strPlaintext = strPlaintext .. strCurrentChar
    ::continue::
  end
  return strPlaintext
end



strAlphaLower = 'abcdefghijklmnopqrstuvwxyz'
print(Encrypt('abcdefghijklmnopqrstuvwxyz', 8))
print(Decrypt(strCiphertext, 8))
print(Encrypt('The cat sat on the mat.', 8))
print(Decrypt(strCiphertext, 8))

Generated Dart Code

var strCiphertext, strCurrentChar, intPosition, strAlphaLower, intDelta, i, strPlaintext;

/// Encrypts with Caesar cipher
dynamic Encrypt(strPlaintext, intDelta) {
  strCiphertext = '';
  var i_end = strPlaintext.length;
  num i_inc = 1;
  if (1 > i_end) {
    i_inc = -i_inc;
  }
  for (i = 1; i_inc >= 0 ? i <= i_end : i >= i_end; i += i_inc) {
    strCurrentChar = strPlaintext[(i - 1)];
    intPosition = strAlphaLower.indexOf(strCurrentChar) + 1;
    if (intPosition < 1) {
      strCiphertext = [strCiphertext, strCurrentChar].join();
      continue;
    }
    intPosition = intPosition + intDelta;
    if (intPosition > 26) {
      intPosition = (intPosition is num ? intPosition : 0) + -26;
    }
    strCurrentChar = strAlphaLower[(intPosition - 1)];
    strCiphertext = [strCiphertext, strCurrentChar].join();
  }
  return strCiphertext;
}

/// Decrypts Caesar cipher
dynamic Decrypt(strCiphertext, intDelta) {
  strPlaintext = '';
  var i_end2 = strCiphertext.length;
  num i_inc2 = 1;
  if (1 > i_end2) {
    i_inc2 = -i_inc2;
  }
  for (i = 1; i_inc2 >= 0 ? i <= i_end2 : i >= i_end2; i += i_inc2) {
    strCurrentChar = strCiphertext[(i - 1)];
    intPosition = strAlphaLower.indexOf(strCurrentChar) + 1;
    if (intPosition < 1) {
      strPlaintext = [strPlaintext, strCurrentChar].join();
      continue;
    }
    intPosition = (intPosition - intDelta) + 26;
    if (intPosition > 26) {
      intPosition = (intPosition is num ? intPosition : 0) + -26;
    }
    strCurrentChar = strAlphaLower[(intPosition - 1)];
    strPlaintext = [strPlaintext, strCurrentChar].join();
  }
  return strPlaintext;
}


main() {
  strAlphaLower = 'abcdefghijklmnopqrstuvwxyz';
  print(Encrypt('abcdefghijklmnopqrstuvwxyz', 8));
  print(Decrypt(strCiphertext, 8));
  print(Encrypt('The cat sat on the mat.', 8));
  print(Decrypt(strCiphertext, 8));
}

Copy of Output

ijklmnopqrstuvwxyzabcdefgh
abcdefghijklmnopqrstuvwxyz
Tpm kib aib wv bpm uib.
The cat sat on the mat.
PrevGreen03.png
NextGreen03.png
UpGreen03.png
Programming - a skill for life!

Suggestions, with examples such as Caesar cipher and Fibonacci sequence, for Blockly programs that you could develop

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    XML, image and generated Smart Pascal code of demonstration of drawing with characters
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    XML, image and generated Smart Pascal code of example of random selection of array elements
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    XML, image and generated Smart Pascal code of demonstration of Caesar Cipher
  4. The Fibonacci Sequence
    XML, image and generated Smart Pascal, JavaScript and Python code of program that outputs the Fibonacci sequence
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    XML, image and generated Smart Pascal (and JavaScript and Python) code of demonstration of insertion sort
  6. Merging Sorted Arrays
    XML, image and generated Smart Pascal code of demonstration of merging sorted arrays
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