From 5c3716ff99b161b7560e1eb01ad2c585af5fbcf1 Mon Sep 17 00:00:00 2001
From: Glen Whitney <glen@studioinfinity.org>
Date: Sun, 31 Jul 2022 09:13:41 -0700
Subject: [PATCH] refactor: Avoid use of a "magic string " 'T'

---
 src/core/PocomathInstance.mjs | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/core/PocomathInstance.mjs b/src/core/PocomathInstance.mjs
index 8cb572b..901514b 100644
--- a/src/core/PocomathInstance.mjs
+++ b/src/core/PocomathInstance.mjs
@@ -5,6 +5,8 @@ import {subsetOfKeys, typesOfSignature} from './utils.mjs'
 
 const anySpec = {} // fixed dummy specification of 'any' type
 
+const theTemplateParam = 'T' // First pass: only allow this one exact parameter
+
 export default class PocomathInstance {
    /* Disallowed names for ops; beware, this is slightly non-DRY
     * in that if a new top-level PocomathInstance method is added, its name
@@ -339,7 +341,7 @@ export default class PocomathInstance {
     * We will start this out very simply: the special string `T` is always
     * a template parameter, and that's the only one
     */
-   _templateParam(t) { return t === 'T' }
+   _templateParam(t) { return t === theTemplateParam }
 
    _addAffect(dependency, dependent) {
       if (dependency in this._affects) {
@@ -401,8 +403,8 @@ export default class PocomathInstance {
       Object.defineProperty(this, name, {configurable: true, value: 'limbo'})
       const tf_imps = {}
       for (const [rawSignature, {uses, does}] of usableEntries) {
-         /* For now, replace 'T' with 'any' */
-         const signature = rawSignature.replaceAll('T', 'any')
+         /* For now, replace theTemplateParam with 'any' */
+         const signature = rawSignature.replaceAll(theTemplateParam, 'any')
          if (uses.length === 0) {
             tf_imps[signature] = does()
          } else {
@@ -413,7 +415,7 @@ export default class PocomathInstance {
                let [func, needsig] = dep.split(/[()]/)
                const needTypes = needsig ? typesOfSignature(needsig) : new Set()
                /* For now, punt on template parameters */
-               if (needTypes.has('T')) needsig = ''
+               if (needTypes.has(theTemplateParam)) needsig = ''
                if (func === 'self') {
                   if (needsig) {
                      if (full_self_referential) {