Adding EqualityComparison (#123)

Author: James Brundage

Transpilers/Syntax/EqualityComparison.psx.ps1

@@ -0,0 +1,56 @@
+<#
+.SYNOPSIS
+    Allows equality comparison.
+.DESCRIPTION
+    Allows most equality comparison using double equals (==).
+
+    Many languages support this syntax.  PowerShell does not.    
+
+    This transpiler enables equality comparison with ==.
+.NOTES
+    This will not work if there is a constant on both sides of the expression
+
+    
+    if ($null == $null) { "this will work"} 
+    if ('' == '') { "this will not"}
+    
+.EXAMPLE
+    Invoke-PipeScript -ScriptBlock {
+        $a = 1    
+        if ($a == 1 ) {
+            "A is $a"
+        }
+    }
+.EXAMPLE
+    {
+        $a == "b"
+    } | .>PipeScript
+#>
+[ValidateScript({
+    # This is valid if the assignment statement's
+    $AssignmentStatementAST = $_
+    # right side is followed by an = and at least one space.
+    $AssignmentStatementAST.Right -match '^=\s{1,}'
+})]
+param(
+# The original assignment statement.
+[Parameter(Mandatory,ValueFromPipeline)]
+[Management.Automation.Language.AssignmentStatementAst]
+$AssignmentStatementAST
+)
+
+process {
+    # This is a very trivial transpiler.
+    
+    # We create a new script by:
+    $newScript =
+        # taking the left side as-is.
+        $AssignmentStatementAST.Left.Extent.ToString() + 
+        # replacing the = with ' -eq '
+        ' -eq ' +
+        # And replacing any the = and any trailing whitespace.
+        ($AssignmentStatementAST.Right.Extent.ToString() -replace '^=\s{1,}')
+    
+    [scriptblock]::Create($newScript)
+}
+