equations: fix five variable names that do not match the equations - #1728
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equations: fix five variable names that do not match the equations#1728Wiljea wants to merge 1 commit into
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Five entries in the documented variable lists name something no equation ever uses, because the equation spells it differently. A reader looking up a variable finds a name that does not exist. Columns and Beams o -> ε the equation reads (ε_cm) Electricity ∈r -> εr U+2208 ELEMENT OF for U+03B5 Forces and Energy Θ -> θ capital for small theta Optics Ix0 -> I₀x the equation reads I₀x_(W/m²) Solid State Devices ID, IDS -> two entries The Electricity one is the least visible: the list carried U+2208 ELEMENT OF where the equations use U+03B5 GREEK SMALL LETTER EPSILON. The two are near-identical on screen. The Optics entry also had a typo in its description, "X rayx", corrected to "X rays" in passing. The last was a single list entry holding two names, so IDS had no entry of its own. Both are used - ID once, IDS three times - and the section header already announced 54 variables while the list held 53, so splitting the entry makes the count correct rather than changing it. Found by a reverse audit: for each documented variable, look for a use in the equation table of src/equations.cc, matching on a boundary so that Md is not satisfied by Md1. Eleven more entries have no use, but they are not errors of this kind - nine belong to the Gases equations that are left commented out in the file, and two (ΔI, Md) have no obvious counterpart and are left alone. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Five entries in the documented variable lists name something no equation ever uses, because the equation spells it differently. A reader looking a variable up finds a name that does not exist.
oε— as in(ε_cm)∈rεrΘθIx0I₀x— as inI₀x_(W/m²)ID, IDSThe Electricity one is worth a second look
The list carried U+2208 ELEMENT OF where the equations use U+03B5 GREEK SMALL LETTER EPSILON. The two are near-identical on screen, which is presumably how it survived.
Untouched by this: the sections that use U+03F5 GREEK LUNATE EPSILON SYMBOL keep it. Electromagnetism spells its epsilon U+03B5, the fluid sections spell theirs U+03F5, and that distinction is deliberate.
The Solid State Devices one changes a count, in the right direction
That entry held two names in one line, so
IDShad no entry of its own. Both are used by the equations —IDonce,IDSthree times.The section header already announced 54 variables while the list held 53. Splitting the entry makes the header correct rather than making it wrong.
How they were found
A reverse audit rather than a reading: for each documented variable, look for a use in the equation table of
src/equations.cc, matching on a character boundary so thatMdis not satisfied byMd1.Eleven further entries have no use anywhere, but they are not errors of this kind and are left alone:
ρr,ρri,ρrf,Pr,Pri,Prf,Tr,Tri,trf— belong to the equations that are left commented out in the file, with the note "These 3 eqns will be substitute in a closed form for Z". They are waiting on a decision, not broken.ΔIin Electricity andMdin Rocketry have no obvious counterpart. Possibly stale, possibly named something I did not think to look for.One unrelated off-by-one turned up while checking: the Waves header announces 39 variables for a list of 40. Not touched here, to keep this diff to one thing.
Also in this PR
help/db48x.mdandhelp/db50x.mdregenerated, since they are built from the source above.