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October 11, 2016 04:47
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parser function for sbn compiler
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function parser (tokens) { | |
var AST = { | |
type: 'Drawing', | |
body: [] | |
} | |
// extract a token at a time as current_token. Loop until we are out of tokens. | |
while (tokens.length > 0){ | |
var current_token = tokens.shift() | |
// Since number token does not do anything by it self, we only analyze syntax when we find a word. | |
if (current_token.type === 'word') { | |
switch (current_token.value) { | |
case 'Paper' : | |
var expression = { | |
type: 'CallExpression', | |
name: 'Paper', | |
arguments: [] | |
} | |
// if current token is CallExpression of type Paper, next token should be color argument | |
var argument = tokens.shift() | |
if(argument.type === 'number') { | |
expression.arguments.push({ // add argument information to expression object | |
type: 'NumberLiteral', | |
value: argument.value | |
}) | |
AST.body.push(expression) // push the expression object to body of our AST | |
} else { | |
throw 'Paper command must be followed by a number.' | |
} | |
break | |
case 'Pen' : | |
... | |
case 'Line': | |
... | |
} | |
} | |
} | |
return AST | |
} | |
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