Editorial: Recast "Abstract Relational Comparison" (#2378)

... as a proper abstract operation, named IsLessThan.

Author: jmdyck

spec.html

@@ -1382,7 +1382,7 @@ <h1>Numeric Types</h1>
             </td>
             <td>
               <emu-xref href="#sec-relational-operators" title></emu-xref>,
-              via <emu-xref href="#sec-abstract-relational-comparison" title></emu-xref>
+              via <emu-xref href="#sec-islessthan" title></emu-xref>
             </td>
             <td>
               Boolean or *undefined* (for unordered inputs)
@@ -5240,9 +5240,9 @@ <h1>SameValueNonNumeric ( _x_, _y_ )</h1>
       </emu-alg>
     </emu-clause>
 
-    <emu-clause id="sec-abstract-relational-comparison" aoid="Abstract Relational Comparison">
-      <h1>Abstract Relational Comparison</h1>
-      <p>The comparison _x_ &lt; _y_, where _x_ and _y_ are values, produces *true*, *false*, or *undefined* (which indicates that at least one operand is *NaN*). In addition to _x_ and _y_ the algorithm takes a Boolean flag named _LeftFirst_ as a parameter. The flag is used to control the order in which operations with potentially visible side-effects are performed upon _x_ and _y_. It is necessary because ECMAScript specifies left to right evaluation of expressions. The default value of _LeftFirst_ is *true* and indicates that the _x_ parameter corresponds to an expression that occurs to the left of the _y_ parameter's corresponding expression. If _LeftFirst_ is *false*, the reverse is the case and operations must be performed upon _y_ before _x_. Such a comparison is performed as follows:</p>
+    <emu-clause id="sec-islessthan" aoid="IsLessThan" oldids="sec-abstract-relational-comparison">
+      <h1>IsLessThan ( _x_, _y_ [ , _LeftFirst_ ] )</h1>
+      <p>The abstract operation IsLessThan takes arguments _x_ (an ECMAScript language value) and _y_ (an ECMAScript language value), and optional argument _LeftFirst_ (a Boolean). It provides the semantics for the comparison _x_ &lt; _y_, returning *true*, *false*, or *undefined* (which indicates that at least one operand is *NaN*). The _LeftFirst_ flag is used to control the order in which operations with potentially visible side-effects are performed upon _x_ and _y_. It is necessary because ECMAScript specifies left to right evaluation of expressions. The default value of _LeftFirst_ is *true* and indicates that the _x_ parameter corresponds to an expression that occurs to the left of the _y_ parameter's corresponding expression. If _LeftFirst_ is *false*, the reverse is the case and operations must be performed upon _y_ before _x_. It performs the following steps when called:</p>
       <emu-alg>
         1. If the _LeftFirst_ flag is *true*, then
           1. Let _px_ be ? ToPrimitive(_x_, ~number~).
@@ -17184,8 +17184,7 @@ <h1>Runtime Semantics: Evaluation</h1>
         1. Let _lval_ be ? GetValue(_lref_).
         1. Let _rref_ be the result of evaluating |ShiftExpression|.
         1. Let _rval_ be ? GetValue(_rref_).
-        1. Let _r_ be the result of performing Abstract Relational Comparison _lval_ &lt; _rval_.
-        1. ReturnIfAbrupt(_r_).
+        1. Let _r_ be ? IsLessThan(_lval_, _rval_).
         1. If _r_ is *undefined*, return *false*. Otherwise, return _r_.
       </emu-alg>
       <emu-grammar>RelationalExpression : RelationalExpression `&gt;` ShiftExpression</emu-grammar>
@@ -17194,8 +17193,7 @@ <h1>Runtime Semantics: Evaluation</h1>
         1. Let _lval_ be ? GetValue(_lref_).
         1. Let _rref_ be the result of evaluating |ShiftExpression|.
         1. Let _rval_ be ? GetValue(_rref_).
-        1. Let _r_ be the result of performing Abstract Relational Comparison _rval_ &lt; _lval_ with _LeftFirst_ equal to *false*.
-        1. ReturnIfAbrupt(_r_).
+        1. Let _r_ be ? IsLessThan(_rval_, _lval_, *false*).
         1. If _r_ is *undefined*, return *false*. Otherwise, return _r_.
       </emu-alg>
       <emu-grammar>RelationalExpression : RelationalExpression `&lt;=` ShiftExpression</emu-grammar>
@@ -17204,8 +17202,7 @@ <h1>Runtime Semantics: Evaluation</h1>
         1. Let _lval_ be ? GetValue(_lref_).
         1. Let _rref_ be the result of evaluating |ShiftExpression|.
         1. Let _rval_ be ? GetValue(_rref_).
-        1. Let _r_ be the result of performing Abstract Relational Comparison _rval_ &lt; _lval_ with _LeftFirst_ equal to *false*.
-        1. ReturnIfAbrupt(_r_).
+        1. Let _r_ be ? IsLessThan(_rval_, _lval_, *false*).
         1. If _r_ is *true* or *undefined*, return *false*. Otherwise, return *true*.
       </emu-alg>
       <emu-grammar>RelationalExpression : RelationalExpression `&gt;=` ShiftExpression</emu-grammar>
@@ -17214,8 +17211,7 @@ <h1>Runtime Semantics: Evaluation</h1>
         1. Let _lval_ be ? GetValue(_lref_).
         1. Let _rref_ be the result of evaluating |ShiftExpression|.
         1. Let _rval_ be ? GetValue(_rref_).
-        1. Let _r_ be the result of performing Abstract Relational Comparison _lval_ &lt; _rval_.
-        1. ReturnIfAbrupt(_r_).
+        1. Let _r_ be ? IsLessThan(_lval_, _rval_).
         1. If _r_ is *true* or *undefined*, return *false*. Otherwise, return *true*.
       </emu-alg>
       <emu-grammar>RelationalExpression : RelationalExpression `instanceof` ShiftExpression</emu-grammar>
@@ -17663,7 +17659,7 @@ <h1>ApplyStringOrNumericBinaryOperator ( _lval_, _opText_, _rval_ )</h1>
         <p>No hint is provided in the calls to ToPrimitive in steps <emu-xref href="#step-binary-op-toprimitive-lval"></emu-xref> and <emu-xref href="#step-binary-op-toprimitive-rval"></emu-xref>. All standard objects except Date objects handle the absence of a hint as if ~number~ were given; Date objects handle the absence of a hint as if ~string~ were given. Exotic objects may handle the absence of a hint in some other manner.</p>
       </emu-note>
       <emu-note>
-        <p>Step <emu-xref href="#step-binary-op-string-check"></emu-xref> differs from step <emu-xref href="#step-arc-string-check"></emu-xref> of the Abstract Relational Comparison algorithm, by using the logical-or operation instead of the logical-and operation.</p>
+        <p>Step <emu-xref href="#step-binary-op-string-check"></emu-xref> differs from step <emu-xref href="#step-arc-string-check"></emu-xref> of the IsLessThan algorithm, by using the logical-or operation instead of the logical-and operation.</p>
       </emu-note>
     </emu-clause>
 
@@ -27722,7 +27718,7 @@ <h1>Math.max ( ..._args_ )</h1>
           1. Return _highest_.
         </emu-alg>
         <emu-note>
-          <p>The comparison of values to determine the largest value is done using the Abstract Relational Comparison algorithm except that *+0*<sub>𝔽</sub> is considered to be larger than *-0*<sub>𝔽</sub>.</p>
+          <p>The comparison of values to determine the largest value is done using the IsLessThan algorithm except that *+0*<sub>𝔽</sub> is considered to be larger than *-0*<sub>𝔽</sub>.</p>
         </emu-note>
         <p>The *"length"* property of the `max` method is *2*<sub>𝔽</sub>.</p>
       </emu-clause>
@@ -27744,7 +27740,7 @@ <h1>Math.min ( ..._args_ )</h1>
           1. Return _lowest_.
         </emu-alg>
         <emu-note>
-          <p>The comparison of values to determine the largest value is done using the Abstract Relational Comparison algorithm except that *+0*<sub>𝔽</sub> is considered to be larger than *-0*<sub>𝔽</sub>.</p>
+          <p>The comparison of values to determine the largest value is done using the IsLessThan algorithm except that *+0*<sub>𝔽</sub> is considered to be larger than *-0*<sub>𝔽</sub>.</p>
         </emu-note>
         <p>The *"length"* property of the `min` method is *2*<sub>𝔽</sub>.</p>
       </emu-clause>
@@ -33430,9 +33426,9 @@ <h1>SortCompare ( _x_, _y_ )</h1>
               1. Return _v_.
             1. [id="step-sortcompare-tostring-x"] Let _xString_ be ? ToString(_x_).
             1. [id="step-sortcompare-tostring-y"] Let _yString_ be ? ToString(_y_).
-            1. Let _xSmaller_ be the result of performing Abstract Relational Comparison _xString_ &lt; _yString_.
+            1. Let _xSmaller_ be IsLessThan(_xString_, _yString_).
             1. If _xSmaller_ is *true*, return *-1*<sub>𝔽</sub>.
-            1. Let _ySmaller_ be the result of performing Abstract Relational Comparison _yString_ &lt; _xString_.
+            1. Let _ySmaller_ be IsLessThan(_yString_, _xString_).
             1. If _ySmaller_ is *true*, return *1*<sub>𝔽</sub>.
             1. Return *+0*<sub>𝔽</sub>.
           </emu-alg>