Add length function; preserve Number node line numbers

src/core.js

 const AST = require('./ast')
+const OsloError = require('./osloError')
 
 module.exports = {
   '+': (a, b) => new AST.Number({ value: a.value + b.value }),
   '>=': (a, b) => new AST.Boolean({ value: a.value >= b.value }),
   '<=': (a, b) => new AST.Boolean({ value: a.value <= b.value }),
   'list': (...args) => { return new AST.List({ elements: args }) },
+  'length': xs => {
+    if (xs.constructor == AST.List) {
+      return new AST.Number({ value: xs.elements.length })
+    }
+
+    return new OsloError({
+      line: xs.line,
+      message: 'length: argument is not a list'
+    })
+  }
 }

src/parser.js

   }
 
   number() {
+    const token = this.tokenStream.eat(tokenTypes.NUMBER)
     return new AST.Number({
-      value: this.tokenStream.eat(tokenTypes.NUMBER).value,
+      line: token.line,
+      value: token.value,
     })
   }
 

test/coreTest.js

   const tree = helpers.evaluate('(list 1 2 3)')
   t.deepEqual(tree[0], new AST.List({
     elements: [
-      new AST.Number({ value: 1 }),
-      new AST.Number({ value: 2 }),
-      new AST.Number({ value: 3 }),
+      new AST.Number({ value: 1, line: 1 }),
+      new AST.Number({ value: 2, line: 1 }),
+      new AST.Number({ value: 3, line: 1 }),
     ]
   }))
 })
+
+test('length function', t => {
+  t.plan(2)
+
+  let tree = helpers.evaluate('(length (list 1 2 3))')
+  t.deepEqual(tree[0], new AST.Number({ value: 3 }))
+
+  tree = helpers.evaluate('(length 5)')
+  t.deepEqual(
+    tree,
+    new OsloError({
+      line: 1,
+      message: 'length: argument is not a list'
+    })
+  )
+})

test/evaluatorTest.js

   t.plan(3)
 
   let tree = helpers.evaluate('(if #t 1 0)')
-  t.deepEqual(tree[0], new AST.Number({ value: 1 }))
+  t.deepEqual(tree[0], new AST.Number({ value: 1, line: 1 }))
 
   tree = helpers.evaluate('(if #f 1 0)')
-  t.deepEqual(tree[0], new AST.Number({ value: 0 }))
+  t.deepEqual(tree[0], new AST.Number({ value: 0, line: 1 }))
 
   tree = helpers.evaluate('(if (= (+ 4 9) (- 20 7)) (+ 10 9) (- 4 2))')
   t.deepEqual(tree[0], new AST.Number({ value: 19 }))

test/parserTest.js

           function: new AST.Identifier({ name: '+', line: 1 }),
           args: [
             new AST.Identifier({ name: 'n', line: 1 }),
-            new AST.Number({ value: 1 }),
+            new AST.Number({ value: 1, line: 1 }),
           ],
         }),
       }),
-      args: [new AST.Number({ value: 5 })],
+      args: [new AST.Number({ value: 5, line: 1 })],
     }),
   ])
 })