[fpos.operations] clarify meaning of assertions/postconditions in table

Author: Eisenwave

source/iostreams.tex

@@ -1750,7 +1750,7 @@
 \tcode{O(p)}      &
  \tcode{streamoff}      &
  converts to \tcode{offset} &
- \tcode{P(O(p)) == p} \\ \rowsep
+ \tcode{P(O(p)) == p} is \keyword{true} \\ \rowsep
 \tcode{p == q} &
  \tcode{bool} &
  &
@@ -1769,29 +1769,31 @@
 \tcode{p + o} &
  \tcode{P}     &
  \tcode{+} offset   &
- \remarks With \tcode{ql = p + o;}, then: \tcode{ql - o == p}  \\ \rowsep
+ \remarks With \tcode{ql = p + o;}, then:
+   \tcode{ql - o == p} is \keyword{true}  \\ \rowsep
 \tcode{pl += o} &
  \tcode{P\&} &
  \tcode{+=} offset &
  \remarks With \tcode{ql = pl;} before the \tcode{+=}, then:
-   \tcode{pl - o == ql} \\ \rowsep
+   \tcode{pl - o == ql} is \keyword{true} \\ \rowsep
 \tcode{p - o} &
  \tcode{P}     &
  \tcode{-} offset   &
- \remarks With \tcode{ql = p - o;}, then: \tcode{ql + o == p}  \\ \rowsep
+ \remarks With \tcode{ql = p - o;}, then:
+   \tcode{ql + o == p} is \keyword{true}  \\ \rowsep
 \tcode{pl -= o} &
  \tcode{P\&} &
  \tcode{-=} offset &
  \remarks With \tcode{ql = pl;} before the \tcode{-=}, then:
-    \tcode{pl + o == ql} \\ \rowsep
+    \tcode{pl + o == ql} is \keyword{true} \\ \rowsep
 \tcode{o + p} &
  convertible to \tcode{P} &
  \tcode{p + o} &
- \tcode{P(o + p) == p + o} \\ \rowsep
+ \tcode{P(o + p) == p + o} is \keyword{true} \\ \rowsep
 \tcode{p - q}   &
  \tcode{streamoff}      &
  distance       &
- \tcode{p == q + (p - q)}   \\
+ \tcode{p == q + (p - q)} is \keyword{true}   \\
 \end{libreqtab4c}
 
 \pnum