0.2.1

A spec can now be written as several files. merge
composes fragments, each a spec that owns part of the math and reads what
another file declares under given:. override
lays patches over a base, each changing part of it. A named expression adds
itself as a term to a sum with adds_to:, and one fragment sets the objective.
Every fragment typesets on its own, in LaTeX, Typst and Markdown, and gets
advice before any merge: what it reads from another file prints in its legend,
so one component's math can be reviewed without the rest of the model.
PyPSA in 24 files
is the PyPSA spec composed this way, and merges back to the one file.

Nothing a 0.2.0 file or call does stops working. Two rules of the language
are now stated exactly. A consumer that attaches data refuses a null or NaN
parameter value: a coordinate with no value has no row, and inf and -inf
are values (#788). And
dual(c) is the rate at which the optimal objective rises with the right side
of c, for every comparator and under either sense, which is what engines
return (#751).

The pull requests in this release:

Composition

• feat(language): a spec is composed from files that each state part of it, and patched with files that each change part of it (#732)
• feat(language): a term names the sum it adds to with adds_to:, a given: expressions: entry of its own file, and a sum another file defines takes terms too (#763)
• feat(language): merge refuses a second objective, and a composed objective reads a sum that each file adds its part to (#763)
• fix(language): merge and override take a list of files, and its order is the order of the terms and of the patches (#761)
• fix(language): a merged spec's descriptions do not depend on the order the fragments are passed in, and a reader's fills one its owner left out (#739)
• fix(language): a given declaration that leaves out its domain or dtype folds into an introducer that sets one (#768)
• fix(language): a file whose terms read each other's sums is refused at load (#780)
• fix(language): a where that reads a given expression names it as a given expression, not as a variable (#809)
• refactor(language): a term prints as the definition it is, and one rule folds every reading (#738)
• fix(typeset): a term a file adds to a sum keeps its definition line when the expressions are inlined (#766)

Language

• feat(language): two files that state the same spec write one text, and canonical --check fails a file that is not in it (#731)
• feat(language): a named expression may declare the frame it is read over (#741)
• feat(language): a sum names several dimensions in one over= list (#778)
• feat(language): a divisor or a power over parameters may add, so a discount factor is written where it is used (#757)
• feat(language): a parameter value that is null or NaN is refused when the data is attached (#788)
• fix(language): dual(c) is the rate at which the optimal objective rises with the right side of c, so an equality has a sign too (#751)
• fix(language): a cases block with one case may compare expressions in its when: (#795)
• fix(language): a where string names several columns in at's over= and into=, as an expression does (#782)
• fix(language): a macro formal written inside a list takes the name the call binds to it (#779)

Typesetting and advice

• fix(typeset): a substituted term that opens with a minus prints as a subtraction (#759)
• fix(advice): an objective that reads a given expression or an empty sum gets advice rather than a KeyError (#767)

Documentation

• docs(pypsa): a single spec covers every pypsa model class and component (#620)
• docs(pypsa): the pypsa spec is also 24 topic files that merge back to it, each component adding its share of a sum by name (#736)
• docs(pypsa): an efficiency, a rate or a phase shift may change from snapshot to snapshot (#717)
• docs: the composition how-to builds a component library from terms each file adds to a sum (#762)
• docs: the composition how-to shows a sum that one file defines and other files add terms to (#800)
• docs: a file restates a shared dimension as its dtype alone, and merge carries the one description written for it (#743)
• docs(language): a reported quotient is absent where its divisor is zero, whether a solve or the data gave that zero (#765)
• docs(notation): the notation page shows a named expression whose declared frame is wider than its body (#756)
• docs: code examples on the site are readable in light and dark mode, and a diagram shows what mathspec leaves to engines and other tools (#730)
• docs: the site follows the reader's light or dark setting, and a page shows where it sits in the navigation (#727)