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Truth table: Difference between revisions
Added Javascript
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[[image:JavaTruth.jpeg|350px]]
=={{header|Javascript}}==
<lang javascript><!DOCTYPE html><html><head><title>Truth table</title><script>
var elem,expr,vars;
function isboolop(chr){return "&|!^".indexOf(chr)!=-1;}
function varsindexof(chr){
var i;
for(i=0;i<vars.length;i++){if(vars[i][0]==chr)return i;}
return -1;
}
function printtruthtable(){
var i,str;
elem=document.createElement("pre");
expr=prompt("Boolean expression:\nAccepts single-character variables (except for \"T\" and \"F\", which specify explicit true or false values), postfix, with \"&|!^\" for and, or, not, xor, respectively; optionally seperated by whitespace.").replace(/\s/g,"");
vars=[];
for(i=0;i<expr.length;i++)if(!isboolop(expr[i])&&expr[i]!="T"&&expr[i]!="F"&&varsindexof(expr[i])==-1)vars.push([expr[i],-1]);
if(vars.length==0)return;
str="";
for(i=0;i<vars.length;i++)str+=vars[i][0]+" ";
elem.innerHTML="<b>"+str+expr+"</b>\n";
vars[0][1]=false;
truthpartfor(1);
vars[0][1]=true;
truthpartfor(1);
vars[0][1]=-1;
document.body.appendChild(elem);
}
function truthpartfor(index){
if(index==vars.length){
var str,i;
str="";
for(i=0;i<index;i++)str+=(vars[i][1]?"<b>T</b>":"F")+" ";
elem.innerHTML+=str+(parsebool()?"<b>T</b>":"F")+"\n";
return;
}
vars[index][1]=false;
truthpartfor(index+1);
vars[index][1]=true;
truthpartfor(index+1);
vars[index][1]=-1;
}
function parsebool(){
var stack,i,idx;
console.log(vars);
stack=[];
for(i=0;i<expr.length;i++){
if(expr[i]=="T")stack.push(true);
else if(expr[i]=="F")stack.push(false);
else if((idx=varsindexof(expr[i]))!=-1)stack.push(vars[idx][1]);
else if(isboolop(expr[i])){
switch(expr[i]){
case "&":stack.push(stack.pop()&stack.pop());break;
case "|":stack.push(stack.pop()|stack.pop());break;
case "!":stack.push(!stack.pop());break;
case "^":stack.push(stack.pop()^stack.pop());break;
}
} else alert("Non-conformant character "+expr[i]+" in expression. Should not be possible.");
console.log(stack);
}
return stack[0];
}
</script></head><body onload="printtruthtable()"></body></html></lang>
=={{header|Liberty BASIC}}==
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